BYU is all about patience.
Nebraska doesn't appear to have the receivers to out physical the BYU DB's downfield. BYU will give the 5-10 yard outs as long as Armstrong is willing to take them. But, really, going deep on BYU isn't the way to beat them. The DB's aren't real good individually. But, they don't gamble very often.
Is Armstrong going to have the patience to go 12+ plays/drive without trying to get greedy? IMO, that will be the key for him.